In a 22-year study, data were collected on aggressiveness and intellectual functioning in more than 600 subjects, their parents, and their children. Both aggression and intellectual functioning are reasonably stable in a subject's lifetime and perpetuate themselves across generations and within marriage pairs. Aggression in childhood was shown to interfere with the development of intellectual functioning and to be predictive of poorer intellectual achievement as an adult. Early 1Q was related to early subject aggression but did not predict changes in aggression after age 8. On the other hand, differences between early IQ and intellectual achievement in middle adulthood were predictable from early aggressive behavior. A dual-process model was offered to explain the relation between intellectual functioning and aggressive behavior. We hypothesized that low intelligence makes the learning of aggressive responses more likely at an early age, and this aggressive behavior makes continued intellectual development more difficult.Aggression has been demonstrated to be a reasonably stable characteristic from childhood to middle adulthood (Eron, Huesmann, Dubow, Romanoff, & Yarmel, 1987; Huesmann, Eron, Lefkowitz, & Walder, 1984;Olweus, 1979). Furthermore, aggression is a characteristic that perpetuates itself within a family system. Aggressive people are more likely to marry aggressive spouses and raise aggressive children (Huesmann et ah, 1984). However, aggression cannot be considered in isolation from other developing behaviors and characteristics (Eron, 1982). In particular, one must consider the relation between aggression and intellectual functioning.A number of studies have revealed a relation between aggression and poor performance on standardized tests of intellectual ability (Burt, 1925;Caplan, 1965;Glueck & Glueck, 1950;Gordon, 1975;Merrill, 1947;Siebert, 1962). The level of intellectual functioning in delinquents generally falls within the lower half of the IQ distribution, with the average IQ of courtinvolved delinquents 10-12 points below the mean IQ of nondelinquents. This relation, however, may be somewhat inflated because bright delinquents may not be apprehended as often as delinquents of lower intellectual functioning. When the genders are examined separately, one usually finds the same degree of relation between intellectual functioning and delinquency in boys and girls (Jensen, 1980), though boys are much more aggressive on the average.Although socioeconomic factors affect both intellectual abilities and aggressiveness in a child, it has been shown that, indeThe research described here was supported by Grant MH-34410 to Leonard D. Eron and MH-38683 to L. Rowell Huesmann from the National Institute of Mental Health.This article is based on a presentation in the symposium "Consistency of Aggression and Its Correlates over Twenty Years" at the annual convention of the American Psychological Association, Anaheim, California, in August, 1983. Correspondence concerning this article should be addressed...